The present invention relates to a pneumatic control system as well as to a pressure responsive valve assembly for such a control system. More particularly, the present invention relates to a pneumatic pressure responsive valve assembly adapted for use in a pneumatically operated system for reducing certain exhaust gas elements of an engine operated vehicle.
As is known, the spark timing of the engine is advanced proportionally to an engine load by utilizing the vacuum which is generated at the advance port of the carburetor and the advance is increased in proportion to the engine load. Means for accomplishing such an effect comprises a valve assembly which renders ineffective the operation of the spark-timing advancing device until the engine load is increased a predetermined amount, thereby minimizing the emission of harmful gas elements such as NO.sub.x.
The problem with the conventional means is that the rubber valve member of the valve assembly is likely to adhere to the valve seat particularly when the engine temperature is relatively high, thereby resulting in retarded operation or non-operation of the valve member. Thus, it is difficult for the conventional means to achieve the primary object of reducing the objectionable exhaust gas elements.